Treating Tilted Molars Question And Answers

Treating Tilted Molars Question And Answers

Question. Treating tilted molars.

• Uprighting first molars by a fixed appliance.
• Using telescopic crowns.
• Non-rigid connector.
• Mesial half-crowns.

Read And Learn More: Fixed Partial Denture Short Essay Question And Answers

Uprighting first molars by a fixed appliance

• Both the premolars and the canine are banded and tied to a passive stabilizing wire.
• A helical uprighting spring is placed inside the molar band and activated by hooking it over the wire on the anterior segment.
• An open coil spring is used to complete the uprighting.
• After uprighting the molars the tooth preparation is done immediately and the prosthesis is given.

Telescopic Crown

A telescope crown and coping can also be used as a retainer on the distal abutment.

Telescopic Crown Design

• A full crown preparation with heavy reduction is made to follow the long axis of the tilted molar
• An inner metal coping is initially made which is luted to the prepared abutment tooth. Then a crown is made that is luted to the coping.

Telescopic Crown Advantages

• Allows for total coverage of the clinical crown
• Compensates for the discrepancy between the paths of insertion of the abutments.

Telescopic Crown Disadvantage
Require radical tooth preparation.

Non-rigid connector
A full crown preparation is done with the path of insertion parallel to the long axis of the tilted molar.

Non-rigid connector Design
A box is prepared on the distal surface of the premolar to place a keyway.

Non-rigid connector Indication
When the molar exhibits a marked lingual and mesial inclination.

Non-rigid connector Contraindication
In long-span pontics.

Mesial half crown

A mesial half-crown restores the occlusal and mesial surfaces as well as portions of the facial and lingual surfaces.

Preparation of mesial half-crown

A mesial half crown is a three-quarter crown rotated 90° with the distal surface uncovered.

As the second molar is generally over-tapered it needs additional grooves on the buccal and lingual aspects.

Question 47. Telescopic crown.

Telescopic crown Definition

It refers to the use of a primary full coverage casting luted to the prepared teeth with the secondary casting placed over the primary casting.

Telescopic crown Objectives

• To achieve parallelism in multiple crown preparations for fixed partial dentures
• Creates a common path of insertion
• Enables malposed teeth to be used without orthodontic treatment
• Avoids pulpal damage during preparation.

Telescopic crown  Disadvantages

• Additional lab procedures
• Difficulty in achieving esthetics
• Expensive.

Telescopic crown  Advantages

• Allows for total coverage of the clinical crown
• Compensates for the discrepancy between the paths of insertion of the abutments.

Telescopic crown  Design

• A full crown preparation with heavy reduction is made to follow the long axis of the tilted molar

• An inner coping is made to fit the tooth preparation and the crown, which will serve as the retainer for the bridge is fitted over the coping.

Question 48. Finishing and polishing.

Finishing and polishing Definition

• Finishing is the removal of excess restoration material from the margins and contours of restoration and polishing of the restoration
• Polishing is the process of making a prosthesis smooth and glossy.

Advantages of polishing and finishing

• Will limit the accumulation and retention of plaque
• Maintain the health of the supporting periodontal tissues
• A polished surface consists of a microcrystalline or Beilby layer
• This layer helps to keep the surface clean and has high corrosion resistance.

Finishing and polishing Objectives

Zone 1 – internal margin

• An l mm wide band of metal is ideal at the finish lines to prevent the luting agent from dissolution and secondary caries
• A perfect marginal fit is attained by re-flowing the margins of the wax pattern.

Defects

• Small nodules can be removed under a binocular microscope with no. 1/4 round bur
• If extensive damage has occurred, remaking the prosthesis is ideal.

Zone 2 – internal surface

A uniform space of 25–35 microns is required for the even spread of the luting agent.

Defects

• Contact between the internal surface and die needs to be relieved with a small round carbide bur
• Small nodules prevent proper seating of the prosthesis and this needs to be removed in one step
• Seating interferences can be located by the use of water-soluble dies (Liqua-Mark), solvent-based dies (Accufilm), and powdered sprays (Occludet).

Zone 3 – the sprue

The sprue is sectioned with a carborundum separating disk and the casting is refined in the area of its attachment with stones and sandpaper disks.

Zone 4 – proximal contacts

• Proximal contact areas are corrected to maintain contact with the adjacent tooth when tried in the mouth
• Overcontoured areas can be relieved by careful scraping with a scalpel and the casting is adjusted till it seats
• Before adjustments, a thin Mylar articulating film is to be placed between the casting and the adjacent tooth.

Connectors

• The connector should be parabolic-shaped
• Finishing can be done with rubber wheels to access the cervical aspect of the connector
• Final polishing can be achieved by a piece of twine.

Zone 5 – occlusal surface

The occlusal contacts are checked with thin Mylar articulating film to ensure that the same contacts as during tryin are present.

Finishing

• If occlusal adjustment is required, they are done with flame-shaped finishing burs or diamonds
• Before adjustments are done the thickness of the metal needs to be assessed.

Polishing

• Done with rouge on a soft brush wheel
• Matt finish can be achieved by air-abrasion with 25- to 50-micron alumina particles for one second.

Zone 6 – axial walls

After finishing the axial walls, they should be smoothly contoured and highly polished, for good oral hygiene maintenance.

Finishing
Is done by grinding with abrasive particles bound on a rubber wheel, or paper disk, or by an abrasive paste with light pressure.

Polishing
A high polish is achieved by polishing using the jeweler’s rouge on the wheel or brush with heavier pressures and higher rotational speeds than for finishing procedures.

Zone 7 – external margins

• A highly polished metal surface without ledges or steps is to be obtained
• Those parts of the margin that cannot be finished on the tooth are finished on the die.

Finishing
Margins should be finished without distortion with a stone gently brushed over the surface.

Polishing

• A soft rubber wheel is used followed by rouge on a brush, with the margin supported with a finger
• After polishing, the residues left by polishing agents need to be removed with a soft toothbrush, by ultrasonic cleaning, or by steam cleaning.

Abrasives used for Polishing and Finishing

• Diamond
• Emery – mixture of aluminum oxide and iron oxide bound to paper discs with glue or resins (used on gold or porcelain)
• Aluminum oxide
• Garnet – For metal and porcelain
• Sandpaper discs are made from a dense crystalline form of quartz, called flint
• Tripoli — A fine siliceous polishing powder combined with a wax binder to form light brown cakes used with a cloth buff wheel or a soft bristle brush
• Rouge – Composed of iron oxide (cake form). Used for gold restorations applied with a soft bristle brush or muslin buff wheel
• Electrochemical finishing — Aqua regia (one part nitric acid and three parts hydrochloric acid)
• Electrochemical milling (stripping): The casting is placed in cyanide solution which etches the casting by removing a layer of 40 microns from Type III alloy in one minute.

Equipment for gold finishing and polishing

Small nodules

Tip of a No 330 bur in a high-speed handpiece.

Smoothening of sprue area

No 2 Craytex disc followed by Burlew wheel.

Base-metal finishing and polishing

High-speed handpiece, straight handpiece, disc on the mandrel, No 2 round bur, No 8 coral stone on the mandrel, aluminum oxide tapered stone, aluminum oxide inverted cone, and No 330 bur.

Internal aspects nodule

No 330 bur.

Surfaces around the sprue

No 8 aluminum oxide coral wheel on a mandrel.

Occlusal grooves smoothening

No 2 carbide bur.

Rough finishing of all accessible areas

No 8 aluminum oxide coral wheel.

Occlusal morphology finishing

Aluminum oxide tapered stone and inverted cone.

Margin finishing

A Spratley knife or white polishing stone and petrolatum followed by a cuttle disc increases marginal adaptation.

Final finishing

Tripoli on a soft Robinson bristle brush with the handpiece running in reverse followed by another soft bristle brush used with rouge.

Question 49. Mention the anatomical concerns for implant placement in the posterior maxilla and mandible region.

For the success of implant in posterior maxilla:

• They should be placed within the bone entirely
• Should be placed away from anatomic structures like the maxillary sinus and inferior alveolar canal
• Ideally, 10 mm of vertical bone and 6 mm of horizontal bone should be available for implant.

Implant placement in the posterior maxilla and specific concerns

• The bone in this region is less dense. It has a thinner cortex and larger marrow spaces than the posterior mandible.
• A minimum of 6 months is required for adequate osseointegration.
• The maxillary sinus is usually close to the edentulous ridge due to the resorption of bone and pneumatization of the sinus.
• A 1 mm gap of bone must be left between the implant and the sinus floor.

Adequate bone height is generally present between the nasal cavity and the maxillary sinus. If the bone height is inadequate augmentation like sinus lift should be considered.

Limitations in Implant placement in the posterior mandible

• The inferior alveolar nerve traverses the mandibular body in this region and treatment planning must allow for a 2.0 mm margin from the apex of the implant to the superior aspect of the canal
• If adequate length is not present generally an implant is not done here. If overlooked, numbness of the lower lip and nerve damage are potential complications
• The width of the residual ridge must be carefully evaluated in the posterior mandible
• Attachment of the mylohyoid muscle and a deep depression present on the lingual aspect must be noted; if this is overlooked, lingual perforation would result.

Question 50. Pickling.

Pickling is a process that removes a surface film from the casting, which has dark surface oxides and tarnish.

Cause of oxide formation on casting

When the cast gold alloys are quenched to retain their superior physical properties, the water that contacts the hot investment causes a reaction that makes the investment soft and granular. This causes a darkening of the casting.

Advantages of pickling

• Removes any clinging investment
• Removes the oxide coating and tarnish.

Disadvantage of using Hydrochloric acid

Fumes from the acid corrode office and laboratory metals.

Other agents that can be used are

• Solution of sulphuric acid with traces of potassium dichromate
• Ultrasonic cleaners.

Pickling Procedure

The discolored casting is heated in an acid such as 50% hydrochloric acid for gypsum-bonded investments.

Method

The casting is placed in a test tube or dish and heated acid is poured over the casting. The acid is poured off and the casting is removed.
The pickling solution should be renewed frequently.

Rules to follow

• Casting if gripped with steel tongs will get contaminated because the pickling solution contains small amounts of copper dissolved from previous castings which when contacted by the tongs deposits copper on the casting.
• The casting if heated can melt the delicate margin or when plunged into the acid, the casting can get distorted by sudden temperature variation.
• After pickling, the casting should be washed thoroughly to remove traces of the acid.